The invention relates to a disposable injector with a housing in which or on which are arranged, in each case at least in some areas, at least one mechanical spring energy reservoir, at least one cylinder/piston unit that can be filled at least temporarily with active substance, at least one piston-actuating ram and at least one trigger unit, in which the spring energy reservoir comprises at least one pre-tensioned spring element and in which at least part of the piston-actuating ram is positioned between the spring energy reservoir and the piston of the cylinder/piston unit.
An injector of this kind, among other things, is known from EP 0 710 130 B1. It is constructed in such a way that the individual structural groups, namely the spring energy reservoir, cylinder/piston unit and trigger unit, cannot be separated from one another or handled separately. The trigger unit has a catch mechanism in which a slide that is moved transversely with respect to the centre line of the injector blocks or releases the piston-actuating ram via a notch or a thread groove.
DE 10 2004 060 146 A1 discloses an auto-injector for an automatic injection of an effective substance, comprising an elongated housing, an injection needle which is axially movably disposed in the housing and is connectable to an effective substance container, a piston which is movably disposed in the effective substance container for discharging the effective substance and a needle protection tube slidably disposed in the housing. A locking member is provided which, in a locking position, prevents movement of the effective substance container relative to the housing. However, the locking member can be brought, by displacement of the needle protection tube into the housing, into a release position in which movement of the effective substance container with respect to the housing is possible.
WO 03/092771 A1 discloses an injection device comprising:
a housing for accommodating a syringe which includes a bore in a front area, a needle which is in communication with the bore through the front area as well as a discharge or, respectively dosing piston, which is movable in the bore relative to the front area in order to discharge the content of the syringe via the needle, wherein the housing has at one end thereof an opening through which the needle can extend;
a spring member, in order to pre-tension the syringe and the needle inwardly relative to the housing;
a drive element which is movable toward the one end for moving the needle of the syringe out of the opening and to move the discharge or, respectively, dosing piston of the syringe toward the front area;
a mechanism which is operable to release the syringe so that the needle moves inwardly with respect to the housing;
a drive coupling extending from the drive element to the discharge or, respectively, dosing piston of the syringe for transmitting a movement of the drive element to the discharge or, respectively dosing piston, wherein the drive coupling is longitudinally compressible.
When the drive element has moved the discharge or, respectively, dosing piston to the front, the drive coupling becomes slowly shorter and transmits a force sufficient to maintain the needle in its extended position while the discharge or, respectively, dosing piston is retained at the front until the mechanism releases the syringe.
Another design of an injection device with a needle and several corresponding syringes is known from WO 2007/002 052 A2.
The object of the present invention is therefore to develop a disposable injector of modular design which, with a small overall size, comprises only a small number of structural parts and, while being easy to handle, ensures safe storage and reliable operation.